java链表

链表是一种物理存储上的非连续存储结构，数据元素的逻辑是通过链表中的引用链接次序实现的，

在这里整理了一线单链表的增删改查。

package seqList;
public class SinglelinkList {
    private int size;
    private Node head;
    class Node{
        int val;
        Node next;
        public Node(int val){
            this.val=val;
        }

    }
    public void addFirst(int val){
        Node node=new Node(val);
        if (head==null){
            head=node;
        }else {
            node.next=head;
            head=node;
        }
        size++;

    }
    public void addIndex( int index,int  val){
        if (index<0||index>size){
            System.err.println("error");
        }
        if(index==0){
            addFirst(val);
            return;
        }
        Node node =new Node(val);
        Node prev=head;
        for (int i = 0; i < index-1; i++) {
            prev=prev.next;

        }
        node.next=prev.next;
        prev.next=node;
        size++;



    }
    public  void addLast(int val){

        addIndex(size,val);

    }
    public int get(int index){
        if (rangecheck(index)){
            Node node=head;
            for (int i = 0; i < index;i++) {
                node=node.next;
            }
            return node.val;

        }else {
            System.err.println("error");
            return -1;
        }



    }
    public boolean rangecheck(int index){
        if(index<0||index>size){
            return false;
        }
        return true;
    }
    public void set(int index,int new_val){
        if(rangecheck(index)){
        Node node=head;
        for (int i = 0; i < index; i++) {
            node=node.next;

        }
        node.val=new_val;



        }else {
            System.err.println("error");
        }

    }
    public void removeIndex(int index){


        if (rangecheck(index)) {
            if (index == 0) {
                Node temp = head;
                head = head.next;
                temp.next = null;
                size--;
            } else {
                Node prve = head;
                for (int i = 0; i < index - 1; i++) {
                    prve = prve.next;
                }
                Node cur = prve.next;
                prve.next = cur.next;
                cur.next = null;
                size--;
            }
        }
    }
    public void removeFist(){
        removeIndex(0);
    }
    public void removeLast(){
        removeIndex(size-1);
    }
    public void removevalonce(int val){
        Node prev=head;
        for (int i = 0; i < size; i++) {
            if (prev.next.val==val){
                Node cur=prev.next;
                prev.next=cur.next;
                cur.next=null;
                size--;
                return;
            }
            prev=prev.next;

        }

    }
    public void removevalAll(int val){
        while (head!=null&&head.val==val){
            Node temp=head;
            head=temp.next;
            temp.next=null;
            size--;
        }
        if (head==null){
            return;
        }else {
            Node prve=head;
            while (prve.next!=null){
                if (prve.next.val==val){
                    Node cur=prve.next;
                    prve.next=cur.next;
                    cur.next=null;
                    size--;
                }else {
                    prve=prve.next;
                }
            }
        }
    }
    public  String toString(){
        String str="";
        Node node=head;
        while (node!=null){
            str+=node.val;
            str+="->";
            node=node.next;
        }
        str+="null";
        return str;
    }

}